1. Technical Field
This disclosure relates to semiconductor processing, and more particularly, to a method for crystallizing a perovskite layer, such as, barium strontium titanium oxide (BSTO), by employing a low temperature process.
2. Description of the Related Art
To be employed as a high dielectric material in semiconductor devices, such as dynamic random access memories (DRAMs), barium strontium titanium oxide (BSTO) films need to be crystallized. The high crystallization temperature of BSTO creates difficulties for integrating BSTO into current semiconductor fabrication processes. Current, BSTO processing includes:
1. Depositing BSTO at high temperature to form crystallized films, as deposited, 450xc2x0 C.-500xc2x0 C. for sputtering and 580xc2x0 C.-640xc2x0 C. for metal oxide chemical vapor deposition (MOCVD); or
2. Annealing the amorphous films deposited at low temperature by annealing at high temperatures (e.g., 600xc2x0 C. or higher.
In most deposition methods, the higher the deposition temperature the better crystalline quality of the film. However, in DRAMs with stacked capacitors, problems occur at high temperatures. For example, oxidation of barrier layers formed to prevent diffusion of metals occurs. Oxidation due to high temperature and the oxygen ambient environment cause an increase in contact resistance for electrical components.
Therefore, a need exists for a method for crystallizing perovskite materials at low temperatures to avoid excessive oxidation and provide a high dielectric constant film.
A method for forming a crystalline dielectric layer deposits an amorphous metallic oxide dielectric layer on a surface. The amorphous metallic oxide dielectric layer is treated with a plasma at a temperature of less than or equal to 400 degrees Celsius to form a crystalline layer.
In other methods, the step of depositing an amorphous metallic oxide dielectric layer on a surface may include the step of depositing the amorphous metallic oxide dielectric layer at a temperature of less than or equal to about 450 degrees Celsius.
The amorphous metallic oxide dielectric layer may include a titanium oxide, such as, barium strontium titanium oxide or other perovskite dielectric. The step of treating may include treating the metallic oxide dielectric layer with a plasma including at least one of nitrogen and oxygen. The plasma is preferably maintained at a pressure of between about 1 mTorr and 5 Torr.
In still other methods, the step of treating may include treating the amorphous metallic oxide dielectric layer with a plasma for less than one minute. The step of depositing metallic oxide dielectric material on the crystalline layer to form a thicker crystalline layer may be included. The crystalline layer preferably provides a non-zero x-ray diffraction intensity from a  less than 111 greater than  surface. The crystalline layer may be employed as a capacitor dielectric in semiconductor devices, such as DRAMs.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.